The striatum, the major entrance of information through the basal ganglia, is the target of two major sources of excitatory afferents, the cerebral cortex and the intralaminar nuclei of the thalamus. Although the role and anatomical organization of the corticostriatal projection has been studied in detail, the importance of the thalamostriatal pathway in the functional circuitry of the basal ganglia remains to be established. To understand better the synaptic interactions that underlie the integration of the thalamic afferents in the neuronal microcircuitry of the striatum, we undertook a research program that aims at elucidating the synaptic connections, the transmitter and the postsynaptic receptors associated with thalamic afferents in the striatum of monkeys. One of our major findings is that thalamic afferents display a high degree of functional and neuronal specificity in the striatum. We demonstrated that thalamic afferents form synapses with specific populations of projection neurons and interneurons in the striatum. These findings have been presented at scientific meetings and published in peer-reviewed manuscripts. These studies will be pursued over the next few years with a particular emphasis on the relationships between thalamic and cortical afferents that converge upon single striatal neurons. These findings will help to understand better the role of the thalamostriatal projection in the functional circuitry of the basal ganglia in primates.